1. Field of the Invention
The present invention relates generally to providing water impenetrable outer cladding to pipeline coatings, and to methods and apparatus for installing same, to better protect joint infill coatings applied to exposed ends of coated pipeline to be laid in bodies of water.
2. Description of the Related Art
It is conventional in the offshore pipeline industry to use weighted coated pipe on pipelines which are being laid on or under the floors of bodies of water. Originally, the weight coatings of each section or length of pipe were of concrete with end metal closure portions of the pipe left bare or unprotected. The end closure portions of adjacent lengths of pipe were welded together on a pipe laying barge as the pipeline was being formed. The bare metal was then covered with a film or sheet of corrosion resistant material. A joint infill resulting from injection of chemicals which reacted and formed an open cell polyurethane foam was then used to fill the annular socket or space between weight coatings. U.S. Pat. Nos. 5,900,195 and 6,402,201, each commonly owned by the assignee of the present application, are examples of this open cell foam infill technology.
More recently, the pipe lengths have been weight coated with a solid synthetic resin, usually being polypropylene and polyethylene synthetic resin coatings to serve as thermal insulation. This has been increasingly the case as offshore production has moved into deeper bodies of water. In some cases a concrete weight coating has been applied on top of the synthetic resin insulation. A similar solid synthetic resin was also desired for the joint infill material. Solid synthetic resins are impenetrable by water; however, concerns have been raised about water ingress through even the relatively small spaces or gaps between the joint infill and the synthetic resin insulation coatings. This has been a particular concern due to the increased hydrostatic pressures beneath bodies of water, particularly in deeper bodies of water.
Other patents, such as U.S. Pat. No. 6,059,319, were directed to forming a cylindrical sleeve seal over the gap between adjacent lengths of plastic coated pipe. Filler panels of butyl rubber, bitumastic, rubberized bitumen or similar materials of a size approximating the interior space within the cylindrical sleeve were used in an attempt to provide corrosion protection. However, gaps and spaces were often present between the various elements, such as between the filler panel material, the pipe coating and the cylindrical sleeve seal. There was thus a risk of fluid leakage and corrosion. For offshore pipelines, particularly in deeper bodies of water, the hydrostatic pressures increased the concerns of fluid leakage through these gaps and spaces and resulting possible corrosion.